CURRENT-CONNECTIONS IN S. HEMISPHERE 307 



in the tropics look to the east, we have often to make a correction 

 for change in latitude. The problem, when re-stated, would be as 

 follows. In the tropics of the Pacific we should expect to find plants 

 of Equatorial South America in Melanesia and North-east Australia ; 

 in those of the Indian Ocean plants of Malaya and North-west 

 Australia on the equatorial coasts of East Africa; and in those 

 of the Atlantic, West African plants on the shores of Brazil and of 

 the Guianas. In the temperate latitudes we should look for Fuegian 

 plants in Cape Colony, Southern Australia, and the northern end of 

 New Zealand ; for South African plants in Southern Australia ; and 

 for plants of the south part of New Zealand in South Chile. We should 

 not look for Australian littoral plants in South America. We will 

 now deal more in detail with these matters : — 



(A) As illustrated in Temperate Latitudes. — When the same littoral 

 plants occur in the cooler latitudes of two of these southern land- 

 masses we are guided by the currents in determining which of the 

 two is the source. Thus, there are two littoral plants, Sophora 

 tetraptera and Convolvulus soldanella, which occur alike in New 

 Zealand and South Chile. This singular distribution is one of the 

 mysteries of the Southern Ocean. Both of them possess buoyant 

 seeds capable of dispersal over an ocean by the currents. Thus, 

 according to my experiments on the seeds of Sophora tetraptera, 

 which I gathered on the Chilian coast, half of them remained afloat 

 after seven months in sea-water and retained their germinative 

 capacity. From results for the seeds of Convolvulus soldanella, which 

 are given in my book on Plant Dispersal (p. 542), it appears that 30 

 per cent, remained afloat after eighteen months in sea- water and 

 subsequently germinated when sown out. Both of these plants 

 are confined to the west side of temperate South America. Since 

 they occur in latitudes north of 42° S. (Ibid., pp. 476-9) they would 

 come within the influence of the northward flowing Peruvian Current 

 and would have no opportunity of doubling Cape Horn. They are 

 found just in those South Chilian latitudes which, as before remarked, 

 would receive New Zealand drift; and we can have no hesitation 

 in regarding them as introduced into South America from New 

 Zealand by the currents. (Both of these plants are treated in detail 

 in my book on Plant Dispersal. The experiments on S. tetraptera 

 were continued after the publication of the earlier work.) 



Yet on the part of Sophora tetraptera there has been an effort to 

 recross the Pacific in warmer latitudes. Not only does it grow in 

 the Juan Fernandez Islands, whither the seeds were probably brought 

 from the southward by the Peruvian Current, but it has been found 

 on Easter Island (lat. 27° S.) in the open ocean. In this last case 

 it would seem that the seeds, after being carried north in the Peruvian 

 Current, came within the influence of the South Equatorial Current. 

 It is not a plant of the tropics, and Easter Island seems to be the 

 northerly limit of its effective dispersal by currents. 



The data indicate the little likelihood of seeds from the temperate 

 or extra-tropical western shores of South America being able to 

 arrive in similar latitudes on the Australian side of the Pacific in an 

 effective condition. Even if the current-connections permitted the 



